Astronomers map spread of dark matter

The Hubble space telescope has mapped out the invisible universe for the first time in 3D – and found that it is lumpy. Astronomers detected so-called “dark matter” that is five times more abundant than the material you can see, formed of atoms, that makes up stars and galaxies.

Their results show that galaxies and clusters of galaxies accumulate in the densest concentrations of dark matter.

The invisible material is spread in filaments like a spider’s web across the universe.

Hubble’s map shows the web stretching halfway back to the beginning of the universe and becoming increasingly lumpy as it collapses under the force of gravity.

Scientists at the California Institute of Technology built the dark matter map by measuring the shapes of half a million distant galaxies.

They detected how the light from the galaxies was distorted and deflected by the invisible material lying in its path before it hit Hubble’s orbiting eye. Astronomers say the challenge was like trying to map a city from aerial photos that showed only streetlights.

They created the map using Hubble’s largest survey yet of the universe – the Cosmic Evolution Survey, or COSMOS – which covers a region of sky nine times the area of the Earth’s moon. Results were combined with observations from some of the biggest telescopes on Earth.

British-born researcher Richard Massey, now at CalTech, said: “It’s reassuring how well our map confirms the standard theories for structure formation.” He described dark matter as the “scaffolding” inside which stars and galaxies have been assembled.

Experts say that mapping dark matter’s distribution in space and time is fundamental to understanding how galaxies grew and clustered over billions of years. The results appeared yesterday this week in the online version of the journal Nature.